nonleaf node represents a test on an attribute, each branch
denotes an outcome of the test and each leaf node shows a
class label. In general, decision trees can be converted into a
set of decision rules as well, by traversing the path from the
root node to a leaf node [28].
Decision rule generation itself alludes to the direct generation
of decision rules without generating a decision tree. An
exemplary decision rule could be: If employee E takes part
in production step S and machine M is used in production
step T then lead times are too high.
For the implementation of the metric-oriented RCA we rely
on decision tree induction as suitable classification technique
due to its high interpretability and the possibility to
deduce decision rules. Yet, additional concepts, esp. pruning
methods, have to be employed to improve the robustness of
decision tree algorithms.
C. Prototypical Implementation and
First Proof of Concept
Our current prototype implements a basic version of the
manufacturing warehouse as well as the metric-oriented
RCA and is based on a dashboard-like GUI. The user selects
a process and corresponding metrics, e. g., lead time or First
Pass Yield, which are represented as speedometers showing
coloured value ranges for each category. That’s enough to
start the metric-oriented RCA. Considering configuration
options, the user can activate tree pruning as well as attribute
filtering. Both simplify the generated tree to enhance its
interpretability.
In the following, we give a short overview of the prototype’s
architecture that we introduced in [7]. On this basis,
we detail on data transformation and pattern detection as the
essential components for the realization of the metricoriented
RCA. Finally, we present a first proof of concept.
Our implementation consists
of three technical layers required
for the metric-oriented RCA
(see Fig. 3): The Data Integration
Layer comprises a relational
version of the Manufacturing
Warehouse. Moreover, we rely
on Java using the WEKA data
mining Framework [33] to implement
not only the Presentation
Layer, i. e., the Cockpit, but
the actual Analytics Layer as
well. The latter comprises Data
Transformation, i. e., Denormalization
and Filtering, as well
as Pattern Detection, i. e., Decision
Tree Induction.
In general, the multidimensional Manufacturing Warehouse
takes an activity-centric view with production step
executions as central facts characterized by various dimensions.
Obligatory flow dimensions describe the process flow
over time and comprise necessary information about time
and process aspects, like the start of a production step and
the manufacturing process it belongs to. Optional context
dimensions comprise additional information regarding employed
resources like machines, manufacturing aids and